Bibliometric Trends and Insights into the Potential of Maize (Zea mays) under the Framework of Conservation Agriculture

Abstract

In spite of the detrimental effects of climate change and decreasing resource efficiency, maize farming is essential to the world’s food and nutritional security. With regard to sustainable maize farming in this environment, conservation agriculture (CA) offers a framework that holds promise in terms of low soil disturbance, perennial soil cover, and sustainable crop rotation. In order to acquire more profound information on the research advancements and publication patterns related to maize under CA scenarios, a bibliometric analysis was conducted. This involved utilizing René Descartes’s Discourse Framework to extract and screen 2587 documents spanning the years 2001 to 2023 from the Dimensions.ai database. The mapping showed that different stakeholders were becoming more interested in maize research under various CA pathways, with a greater emphasis on reaching the second sustainable development target, or “zero hunger”. The most influential journals were “Soil and Tillage Research” and “Field Crops Research”, with 131 and 85 papers with 6861 and 6186 citations, respectively. The performance analysis found “Christian L. Thierfelder” and “Mangi Lal Jat” as the eminent researchers in the areas of maize research under CA. Thus, the International Maize and Wheat Improvement Center (CIMMYT) and the Indian Agricultural Research Institute (IARI) were identified as the important institutions in conducting research pertaining to maize under CA systems, while the United States, India, and Mexico emerged as prominent countries with notable collaboration efforts for imparting research under the given scenarios. Three thematic clusters delineating keywords from three distinct sections—key drivers, objectives, and methodology—were identified through co-word analysis using word clouds, tree maps, and thematic networking of the keywords from the abstract and titles of screened publications. These thematic clusters highlighted the growing emphasis on region-specific studies under CA, particularly in sub-Saharan Africa and the Indo-Gangetic plain, to enhance the resilience of the agri-food system. Therefore, mapping maize’s potentialities within the CA framework has revealed the field’s dynamic nature and offers insightful information to researchers and policymakers that could help them plan future studies and cooperative initiatives aimed at boosting the productivity and sustainability of maize-based systems under the CA framework.

1. Introduction

The dynamic nature of agriculture is increasingly evident in the context of the burgeoning population, global climate change, and the imperative for food security [1]. These challenges necessitate the adoption of a multifaceted approach through resilient and sustainable farming practices, which are not only climate-smart but also fulfill food and nutritional security requirements. Conservation agriculture (CA) offers a viable solution for mitigating the adverse impacts of climate change on agriculture through promoting minimal soil disturbance, maintaining adequate soil cover, and implementing diversified crop rotation [2,3]. Further, intensive conventional tillage (CT) coupled with cropping system intensification often leads to the degradation of soil structure, resulting in the rapid oxidation of soil organic carbon, and the loss of topsoil and nutrients through erosion [4,5]. In the backdrop of the ill effect of CT, CA has increasingly gained attention from various stakeholders due to its numerous agronomic, environmental, and economic benefits [6,7]. The acreage under the CA system is constantly expanding at an annual rate of >10 mha, and the total acreage under CA stands at 205.4 mha, with a share of 14.7% of the global cropped area [8]. The spread of CA has been expanding in Asia, Africa, and Europe in recent years because farmers are becoming better organized in working together and networking. The primary reasons for the shift from CT to CA is the ability of CA to significantly reduce soil erosion, enhancing soil stability and health [9]. In the era of the escalating water crisis and declining nutrient balances in soil due to ongoing climate change, the presence of crop residues and cover crops in CA reduces water evaporation, enhances soil moisture, and in turn enhances the water productivity [10,11], supporting crop growth along with enhanced soil microbial activity and nutrient cycling, leading to better soil fertility and crop productivity over time [12]. Moreover, CA often leads to reduced input costs for farmers, on one hand by lowering fuel, labor, and machinery expenses associated with tillage [13], and on the other by enhancing carbon sequestration and reducing greenhouse gas emissions [14].

With a peak production and productivity of 1210 million tons and 5879 kg/ha, respectively, maize (dry grain) is the second most widely produced crop worldwide, with yearly cultivation on an estimated 206 mha of land. Its cultivation began in the late 19th century [15]. Given that rice and wheat are experiencing area stagnation, maize is predicted to surpass wheat in terms of acreage by 2030. Maize is gaining popularity in the present context of climate change due to its adaptability, high productivity, and nutritional value. Being a C₄ plant, maize has the physiological advantage of a more efficient photosynthetic pathway than many other staple crops, enabling it to better withstand high temperatures and increased atmospheric carbon dioxide levels [16,17]. Furthermore, maize’s relatively short growing season allows it to fit into diverse cropping systems, making it a flexible option for farmers dealing with unpredictable weather patterns [18]. The highest genetic productivity potential of maize requiring much less water to complete its life cycle as compared to other cereals is another crucial factor for its successful adaptation to several newer ecologies [19]. It offers a substantial calorie and biomass yield, which is essential for food security and livestock feed, especially in densely populated or resource-limited regions [20]. Additionally, maize is versatile in its usage, serving as food, feed, and raw material for various industrial products, including biofuels, which are increasingly important in the context of renewable energy [21].

The growth of maize research under the CA system in the twenty-first century has been marked by significant advancements driven by increasing global concerns over food security and sustainable farming practices [22]. In the context of maize, a staple crop critical for food, feed, fodder, and other industrial purposes, research has increasingly focused on optimizing CA practices to improve productivity, input use efficiency, soil health, and resilience to climate change [12,23]. The integration of CA practices in maize cultivation has shown promising results in various regions, including sub-Saharan Africa, Latin America, and parts of Asia, where soil degradation and water scarcity are prevalent challenges [24,25]. Moreover, advancements in breeding and agronomic research, such as the development of drought-tolerant hybrid maize varieties [26] coupled with precision farming techniques encompassing precision input management according to the variability in the field, have further propelled the adoption of CA [27,28]. Collaborative research initiatives among national and international stakeholders in different avenues of research for the propagation of sustainable agri-food systems involving maize have played a crucial role in disseminating knowledge and best practices of maize under CA systems across different agro-ecological zones around the world [29,30]. In the present study, we have hypothesized that the ongoing efforts in maize research under CA are expected to contribute significantly to achieving global food security and environmental sustainability goals in the twenty-first century.

This research study employed text mining and bibliometric analysis to quantitatively evaluate the academic literature on maize under several CA scenarios. Using statistical methods and procedures, trends in bibliographic data—such as publication outputs, citations, co-authorship, and keyword frequency—are analyzed in a bibliometric analysis [31,32]. By looking at patterns, this bibliometric analysis aims to identify research gaps and trends, important journals, and impactful authors along with their total publications and collaborations among researchers, organizations, and countries in the field of maize research under the umbrella of CA systems. This study has the potential to address the following research questions/issues pertaining to maize research under CA:

• What is the connection between the growth in publications and citations of maize under various aspects of CA scenarios?
• What are the overall numbers of articles published in each research area, and what is the subject matter where these articles are most frequently found?
• What significant fluctuations has the literature undergone over time?
• How many articles are linked to a particular SDG under the present theme?
• What is the intellectual framework that highlights the prominent authors and top organizations conducting and publishing agricultural research focusing on the agri-food systems involving maize regarding CA aspects?
• What are the top collaboration networks among authors, organizations, and countries that are engaged in maize research under CA systems?
• What are the implications along with future lines of work of maize research under CA systems subjected to the scenario of decreasing agricultural land coupled with the rapid changing of the global climate?

These pertinent questions highlight the potential existing research gaps in framing the present study to give a proper scientific answer to the above question with support from various scientific methodologies and indicators, which can further direct the research on maize under CA frameworks in a more sustainable way under future lines of work for many researchers and collaborators.

2. Methodology

In the current study, the standard procedure of René Descartes’s Discourse Framework was utilized to retrieve the pertinent literature, filter and analyze the retrieved data, and interpret the findings in order to obtain valuable insights into the body of knowledge on maize research under CA systems.

2.1. René Descartes’s Discourse Framework in Bibliometric Analysis

The application of René Descartes’s Discourse Framework in bibliometric analysis offers a structured and rigorous approach to studying the literature within a given research field. This standard framework primarily emphasizes clarity, systematic doubt, and methodological rigor, and provides a solid foundation for conducting bibliometric studies [33]. The bibliometric analytic process encompasses 4 stages: “doubt”, “partition of problem”, “problem solving”, and “inspection and review”, where it begins with a comprehensive literature search guided by the principles of clarity and precision central to Descartes’s philosophy [34,35,36].

2.1.1. Step 1: Doubt Stage

This involves the critical analysis of the existing literature, where the researchers question the validity, reliability, and comprehensiveness of the sources available. By approaching the literature with a mindset of doubt, researchers can identify gaps, biases, and inconsistencies, thereby laying the foundation for a more thorough and accurate analysis. This stage is crucial for facilitating the careful selection of reliable and relevant sources that ensure our dataset represents the most accurate knowledge base available [36]. It emphasizes ensuring clarity and that the search terms and criteria are well-defined and consistently applied, minimizing the risk of including irrelevant or marginally related studies.

2.1.2. Step 2: Partition of Problem

In order to break down difficult issues into smaller ones, this step describes Descartes’s method of systematic doubt and admits that, in spite of his doubt regarding the existing problem, he cannot reject its existence as a thinking person. Breaking the research question into shorter and smaller manageable sub-themes helps in the essential organization of the literature. Dividing the research issue into segments—theoretically used and supported, methodologically employed, and the findings and trends observed—enables the researchers to systematically go through the aspects in question [37]. This partitioning enhances the likelihood of reviewing all the literature within the individual sections, because when a subdivision in a particular section is exhausted, the next subdivision in the next section will contain literature that is similar to the first subdivision.

2.1.3. Step 3: Problem Solving Approach

In this stage of analysis, Descartes provides the need for skepticism to readdress each piece of knowledge that one acquires, covers the area of mathematics, and thoroughly discusses the work of mathematical reasoning in bibliometric philosophy. As such, he calls for the application of systematic mathematical approaches in the analysis of the literature by assuming comprehension of the material to devise enhanced solutions [38]. This stage is crucial for generating meaningful insights and drawing conclusions about the research landscape.

2.1.4. Step 4: Inspection and Review

This step follows Descartes’s principle of synthesis, in which all results gathered during the analysis phase are integrated to provide an outline of the overall structure of intellectual content in the field. Links with other studies are made, the locales in the current study are pinpointed, and the avenue for further research is outlined [39]. Altogether, in this manner the researchers are able to give substantial information concerning the formation and state of the paradigm in the field at the present stage and its prospects.

Therefore, relying upon the robustness of the method, this study employed Descartes’s four stages of the Discourse Framework by methodically reviewing the body of literature to produce fresh perspectives on maize research under CA systems [40]. The current study progressed through a number of standardized methodological steps involving the “doubt stage” through “retrieving literature”, “problem partitioning” through “record screening”, “problem solving” through “record analysis”, and finally, “inspection and review” through the “interpretation of results”. Hence, it upholds the rigorous standards of scientific inquiry that are essential for advancing knowledge within any research domain.

2.2. Retrieval of Pertaining Literature

An inclusive investigation was undertaken using bibliometric analysis to discern the evolutionary trends and define the boundaries of the specific field of maize research under CA systems following the detailed stages of René Descartes’s Discourse Method, which is clearly highlighted in Figure 1. Conventionally, the Web of Science and Scopus databases were used as the primary source for retrieving the dataset pertaining to a particular field; however, their accessibility was restricted because of the requirement of paid access [41]. Nowadays, the research information and datasets encompassing scholarly publications and their metadata are integrated and available through free access (without a paid subscription) from Dimensions.ai (https://www.dimensions.ai/) (accessed on 17 February 2024), owned and maintained by Digital Science and Research Solutions Inc, Massachusetts Ave Cambridge, United States. [42,43]. Historically, Web of Science (WoS) was the primary source for standardized and uniform research publications [43]. However, Scopus and Google Scholar later emerged as strong alternatives. Due to the financial barriers associated with subscription fees, particularly for individual researchers in developing and underdeveloped nations, Google Scholar became the favored option [44]. The platform allows users to easily access data and build conceptual frameworks. Following the COVID-19 pandemic, the demand for bibliometric studies surged, as the crisis highlighted new requirements for analyzing trends in real time. Dimensions.ai offers researchers the ability to search full-text data across various time periods and includes a wide range of scholarly outputs, such as preprints, journal articles, book chapters, conference papers, monographs, and edited volumes [45]. A comprehensive search string encompassing ‘“Conservation agriculture” AND “Maize” OR “Corn” OR “Zea mays”’ was used in the Dimensions.ai database to retrieve datasets pertaining to maize under CA systems, which resulted in 3709 documents/publications including research articles, book chapters, monographs, conference papers, etc.

2.3. Screening of Retrieved Literature

Further, to clean and sort the original dataset, the search string focused mainly on the “titles, abstract, and keywords”, and for filtering, the publication type was confined to “research article” coupled only with publication year “from 2001 to 2023”. This search string resulted in 2587 documents published between 2001 and 2023, which was further subjected to analysis to map the bibliometric trends in the present study.

2.4. Scientific Analysis of Dataset

The obtained dataset, after performing the specific search string mentioned above, was exported in a comma-separated value (CSV) file for the subsequent scientific bibliometric investigation. For further organization of the data and the visual presentation, “Microsoft Excel”, “VOS viewer software” (version 1.6.20), and the “bibliometrix” package in “R software” (version 4.4.0) were utilized [39,46,47]. To improve the visualization of links among research elements, such as authors, publications, citations, nations, and keywords, two separate methodologies were utilized in the bibliometric analysis: performance analysis and science mapping [31,32].

Performance analysis focuses on assessing the productivity and impact of researchers, institutions, or countries by employing key metrics such as the total number of publications, citation counts, h-index, and other indicators of research output and influence [48]. It helps in identifying leading contributors in a field in terms of researchers as well as sources, recognizing trends in research productivity, and evaluating the effectiveness of research policies and funding. Alternatively, science mapping is a visual representation of the relationships and networks within a specific research field that benefits the identification of the structure and dynamics of scientific disciplines. It includes mapping the intellectual, social, and conceptual structures of research such as citation analysis, co-citation analysis, co-word analysis of authors, countries, organizations, etc., thus providing insights into how different areas of knowledge interconnect and evolve over time [31,32].

The citation analysis, being the fundamental tool in bibliometrics, examines the frequency and patterns of citations received by publications that lead to the identification of highly influential works, traces the development of ideas, and measures the impact of research [31]. Moreover, the co-citation analysis studies the frequency with which two documents are cited together by subsequent publications, uncovering the intellectual structure of a research field, highlighting clusters of related studies, and identifying seminal works that form the foundation of specific research areas [32,49]. Similarly, the co-authorship analysis examines the patterns of collaboration between researchers based on their joint publications to determine the social structure of scientific communities, identifying key collaborators and assessing the extent of interdisciplinary research [50,51]. The co-word analysis investigates the frequency and co-occurrence of keywords in scientific publications through word clouds, tree mapping, thematic networking, etc. to identify exciting research themes, trends, and emerging topics [52,53]. The thematic map was used to categorize different themes of research articles on conservation agriculture related to maize crops based on their degree of development (cohesion within the theme) and degree of relevance (importance of the theme) [54]. These dimensions help interpret the importance (centrality) and the developmental stage (density) of the themes in this context. The spinglass method was used to network the bigrams from the titles of the research articles. The interactions between these spins (nodes) were modeled based on the edges (connections) between nodes [55].

The methods and techniques used in this study are intended to provide readers with a thorough grasp of the state of the research on maize under CA systems and to reveal important information about research themes and trends.

3. Results

3.1. Performance Analysis of Publications

The present performance analysis of documents/publications was undertaken in the context of the conservation agriculture system pertaining to maize for the extracted 2587 documents to determine the five performance metrices viz., the total number of publications from 2001 to 2023, the number of publications in various research categories, the number of publication concerning varying sustainable development goal (SDG) themes, the top 20 influential journals with the most documents published, and the performance of the top 15 most impactful authors/researchers in terms citation count. The performance analysis carried out is explained in the following sections.

3.1.1. Growth Patterns of Total Publications (TPs) over the Years

The advancement of quality publications in the arena of research on maize under CA systems was assessed to comprehend the inclusive performance. The analysis of the progression of the total number of scientific publications from 2001 to 2023 is illustrated in Figure 2. The results displayed a steady increase in the number of publications in the first decade, i.e., from 2001 to 2010, followed by an exponential upsurge in the next decade, i.e., 2011–2020, with a slight decline after 2021. The most number of publications was observed during the 2018–2020 period, with the year 2020 recording 144 research publications, followed by 138 in 2018 and 125 in 2019, indicating a significantly higher interest of researchers as well as stakeholders in the prospects of maize under CA systems in the later part of the 2020s.

3.1.2. Scientific Contributions by Countries

The visualization of the total scientific production of countries involved in maize research publications under CA systems between 2001 and 2023 is shown in Figure 3. It reveals that USA leads in the publication of documents in the present context, with a total of 340 publications, followed by India, France, Australia, Zimbabwe, and South Africa, with 295, 167, 151, 134, and 123 number of publications, respectively.

3.1.3. Count of Total Publications in Various Research Categories and Different Themes of SDGs

As maize is gaining attention as a climate-resilient crop, the comprehensive research on maize under CA systems underscores a wide range of domains involving research interests from researchers and stakeholders of various research fields with multiple diverse objectives. Therefore, to gain inclusive insights from the perspective of individuals and stakeholders’ interest in research on the maize crop, a sound performance analysis was conducted to discover the potential research arenas within this broad field of research. Out of the 2587 research publications/documents analyzed, the spread of publications across different research domains is demonstrated in Figure 4. The results underscore that the “agricultural, veterinary, and food sciences” research domain has the highest number of publications, with 1685 publications, followed by “environmental sciences (616)”, “human society (256)”, and “biological sciences (243)”.

Furthermore, the number of published research documents pertaining to each of the 17 SDGs of the United Nations (UN) is shown in Figure 5. It reveals that among the SDGs, “SDG 2: Zero Hunger” had the highest number of publications, with 1956 documents concentrating on this theme as a research objective. SDG 2 was followed by the “SDG 15: Life on Land” and “SDG 13: Climate Action”, with 545 and 279 publications, respectively, delineating the need for research on maize under CA systems to achieve the UN’s SDGs within the stipulated time frame. These findings accentuate the implication of addressing topics related to achieving global food security and environmental sustainability through climate change adaptation and mitigation via crop diversification to maize under CA scenarios.

3.1.4. The Most Impactful Journals

The top 20 impactful journals that have published the highest number of publications/documents pertaining to maize under CA systems, as determined through performance analysis, is presented in

Table 1. Performance of the most influential journals (top 20) on maize under conservation agriculture from 2001 to 2023.

Sl. No.	Name of Journal	Document Count	Citations	Average Citations per Document
1	Soil and Tillage Research	131	6861	52.4
2	Field Crops Research	85	6186	72.8
3	Agriculture Ecosystems & Environment	74	5648	76.3
4	Agronomy	59	806	13.7
5	Sustainability	55	1830	33.3
6	The Indian Journal of Agricultural Sciences	50	143	2.9
7	International Journal of Agricultural Sustainability	41	2695	65.7
8	Agronomy for Sustainable Development	41	3160	77.1
9	Agricultural Systems	38	1547	40.7
10	South African Journal of Plant and Soil	34	206	6.1
11	The Science of The Total Environment	30	1094	36.5
12	Experimental Agriculture	28	559	20.0
13	Agriculture	28	471	16.8
14	International Journal of Current Microbiology and Applied Sciences	27	68	2.5
15	Geoderma	26	760	29.2
16	Plant and Soil	25	1650	66.0
17	Renewable Agriculture and Food Systems	25	780	31.2
18	Indian Journal of Agronomy	24	10	0.4
19	Land Degradation and Development	23	507	22.0
20	Frontiers in Sustainable Food Systems	23	326	14.2

. The findings indicate the three most impactful journals as “Soil and Tillage Research”, “Field Crops Research”, and “Agriculture Ecosystems & Environment” published by Elsevier with 131, 85, and 74 documents, along with 6861, 6186, and 5648 citations, respectively. However, the highest mean citations per document was recorded by the journal “Agronomy for Sustainable Development” (77.1) followed by “Agriculture Ecosystems & Environment” (76.3), showing their robustness in gaining citations per document or publications.

3.1.5. The Most Influential Authors

Similarly, the 15 most impactful authors in terms of citation counts received by their authored publications on maize under CA systems are showcased in

Table 2. Performance of the most influential authors (top 15) working on maize under conservation agriculture aspects from 2001 to 2023.

Sl. No.	Author’s Name	Organization, Country	Documents	Citations	CP *
1	Christian L. Thierfelder	International Maize and Wheat Improvement Center, Zimbabwe	88	4753	54.0
2	Mangi Lal Jat	International Maize and Wheat Improvement Center, India	88	4504	51.2
3	Bram Govaerts	International Maize and Wheat Improvement Center, Mexico	51	3306	64.8
4	Tapas Kumar Das	Indian Agricultural Research Institute, India	50	1080	21.6
5	Hanuman Sahay Jat	Central Soil Salinity Research Institute, India	44	2199	50.0
6	Chiter Mal Parihar	Indian Agricultural Research Institute, India	44	1030	23.4
7	Nele Verhulst	International Maize and Wheat Improvement Center, Mexico	36	1649	45.8
8	Parbodh Chander Sharma	Central Soil Salinity Research Institute, India	36	2046	56.8
9	Rattan A Lal	The Ohio State University, United States	36	3573	99.3
10	Mahesh Kumar Gathala	International Maize and Wheat Improvement Center, Bangladesh	35	1882	53.8
11	Ranjan Bhattacharyya	Indian Agricultural Research Institute, India	34	1061	31.2
12	Walter Tamuka Mupangwa	International Maize and Wheat Improvement Center, Zimbabwe	33	1271	38.5
13	Marc Corbeels	International Institute of Tropical Agriculture, Kenya	32	3734	116.7
14	Richard William Bell	Murdoch University, Australia	26	541	20.8
15	Shankar Lal Jat	ICAR-Indian Institute of Maize Research, India	25	458	18.3

* CP = citation per document.

. The authors Christian L. Thierfelder, affiliated with the International Maize and Wheat Improvement Center, Zimbabwe, followed by Mangi Lal Jat, affiliated with the International Maize and Wheat Improvement Center, India, were the most impactful authors, with 4753 and 4504 citations, respectively, for 88 documents each. These findings emphasize the substantial contributions made by these esteemed journals and influential authors to the field of maize research under CA towards evolving and propagating the research knowledge and improving the clarity of the understanding of CA in the context of maize.

3.2. Science Mapping of Documents

Science mapping methodologies were utilized to visually represent the intellectual structure and relationships among the research constituents, including authors, keywords, journals, organizations, and countries, using the dataset comprising 2587 documents on maize research under CA systems [31]. These methods made it possible to examine and visualize the relationships and patterns in the data that were gathered, which gave researchers important new perspectives on the state of the field’s scholarship [51].

3.2.1. Visualization of Authors

The key authors and prominent researchers of the screened publications are decisive in their scientific endeavors thanks to their accountability for the conceptualization of methodologies, developing research, the scientific analysis of the generated data, along with the writing, review, and curation of manuscripts [56]. They take sole responsibility for the direct and indirect effects of their experiments/studies, advancing knowledge and disseminating transparent, precise, and impartial research findings [57]. The number of documents was reduced to 263 by keeping a limit of twenty-five authors per document and a minimum of five documents per author to obtain better results regarding collaboration networks by removing authors not contributing much to the field.

Citation Analysis of Authors

To gain deeper insights into the scholarly network of researchers/authors and their scholarly impact, a detailed citation analysis and co-authorship analysis were executed [31,32]. Following a citation analysis that looked at each author’s total number of citations, seven theme clusters were identified and are shown in Figure 6. The authors who had the most citations are shown in blue, while the authors who had the fewest citations are shown in orange. This graphical representation illustrates the many degrees of scholarly influence that authors/researchers have.

Co-Authorship Analysis of Authors

On the other hand, the co-authorship analysis examining the authors’ partnerships in research papers primarily concentrated on the authors’ social network. A wide, interdisciplinary approach is necessary to conduct research on maize under CA systems since they include several researchers/stakeholders. Consequently, researchers no longer work alone to solve problems; instead, they collaborate with each other to gain better insights. Therefore, the co-authorship analysis holds significant implications for the determination of the collaboration network. The analysis shown in Figure 7 reveals 17 clusters with different colors. The largest cluster, i.e., the red-colored one, had 32 researchers, followed by the green cluster with 29 researchers. Every cluster exemplified the researcher’s cooperation and intellectual collaboration with each other. Significant researchers viz., Christian L. Thierfelder, M L Jat, Bram Govaerts, Marc Corbeels, Rattan Lal, etc. are the leading citation holders of the separate clusters, contributing the most scientific contributions in the field of maize research under conservation agriculture. The idea that co-authorship is one of the most quantifiable and well-documented types of scientific cooperation is that these connections result in the creation of a “co-authorship network” [51]. Overall, the citation analysis and co-authorship analysis gave vital information on the scholarly impact and collaborative networks generated among eminent authors in the various schools of maize research under CA landscapes.

3.2.2. Visualization of Journals

Research journals (sources) are quite crucial as they disseminate new scientific knowledge, ensure rigorous peer review, and establish scholarly communication [58]. They enable researchers to stay updated with advancements, fostering academic dialogue and innovation. Moreover, journals contribute to the academic community by validating research quality and providing a reliable source of information [59]. Therefore, to detect the most impactful journal in terms of publishing research articles on maize research under CA systems, the visualization of journals in bibliometric analysis is essential because it simplifies the interpretation of complex data through citation and co-citation analyses. By graphically representing citation patterns of journals/sources, the author collaborations as well as the influential journals in the specific field of research can be easily detected [32]. Here, a total of 808 sources were found, of which 56 impactful sources/journals were filtered out by fixing the minimum number of documents published and the minimum total citations received to ten each.

Citation Analysis of Journals

The overlay visualization of the citation analysis of sources/journals shown in Figure 8 displays the journals as nodes, with their weight/size representing the number of citations received by each journal. The colors of the thematic clusters and nodes signify the year of publications received in the respective journals. Our analysis resulted in the formation of 6 thematic clusters with a maximum of 17 documents each in cluster 1 and cluster 2. The purple-colored cluster that shows its publication trends towards 2016 has the most citations received by the journal “Field Crops Research”, forming 51 links with a link strength of 1501, while during 2018, “Soil and Tillage Research” received the most citations, coded with bluish thematic cluster, comprising 51 links and a link strength of 1413. However, in recent years (2020 onwards), more citations were received by the journals viz., “Sustainability” and “Scientific Reports”, which were colored with a yellow cluster.

Co-Citation Analysis of Journals

The co-citation analysis of journals is pivotal as it reveals relationships between scholarly works by identifying how frequently pairs of articles are cited together [48]. This method uncovers the intellectual structure of research fields, highlighting influential studies and key areas of knowledge integration. It aids in understanding the development of scientific disciplines and the evolution of research themes. The network visualization of the co-citation analysis of journals/sources is crucial as it transforms complex co-citation data into intuitive graphical representations to discern patterns, trends, and clusters of related research [49]. This facilitates the quick identification of core journals, significant research clusters, and emerging topics. Figure 9 visualizes the co-citation network of sources of publications pertaining to maize under CA systems that are recurrently cited together. A total of six clusters have been formed, as seen in the visualization network, which suggests that there are different journal groups that are commonly cited in articles together. The red-colored cluster had the highest number of sources at 70, followed by the green- and blue-colored clusters with 65 and 52 sources, respectively. The journal “Soil and Tillage Research”, being the most cited journal, also appears in both the green and blue clustered networks, representing more occurrences with other diverse groups of articles. Significant insights into the influence and connections between journals in the field of maize research under CA systems may be gained from both the citation analysis and the co-citation analysis.

3.2.3. Visualization of Words

The visualization of word analysis in bibliometric studies is critical as it helps decode the thematic essence and research trends within a body of literature. By mapping the frequency and co-occurrence of words/phrases in titles, abstracts, and keywords, researchers can identify prevalent topics, emerging themes, and shifts in research focus over time [52,53]. This technique also enhances the understanding of the conceptual landscape of a field. Effective visualization transforms complex textual data into clear, interpretable formats such as thematic networks, word clouds, tree maps, etc. [31,60]. These graphical representations enable quick insights into the main subjects and their interconnections, facilitating easier navigation of extensive research corpora. For getting a proper result of desire, the minimum number of occurrences of a phrase/word was fixed up at 50 and some of the unnecessary and generalized words were omitted for analysis which resulted in 142 number of words for final visualization. We analyzed the extracted data employing “creation of map using textual data” option of the VOS viewer software to visualize the extracted words [47]. It resulted in the identification of three thematic clusters, each represented by a node (phrase/word) and links indicating their relationships and the thickness of the link revealing the strength of their links, as shown in Figure 10. The first thematic cluster, i.e., visualized in red shades consisted of 80 phrases/words that recurrently appeared in the titles/abstracts/keywords of the research publications pertaining to maize under CA systems and it comprises the keywords namely “farmer”, “adoption”, “technology”, “climate change”, “resource”, “diversification”, “soil cover”, “policy”, “soil erosion”, etc. The second thematic cluster shaded with green color, visualizes 49 words of importance such as “tillage”, “yield”, “rotation”, “residue”, “carbon”, “biomass”, “residue retention”, “nitrogen”, “cropping season”, etc. indicating the potentialities of these keywords in maize research under CA scenarios. The blue shaded cluster refereeing the third theme consisted of 13 phrases/words involving “efficiency”, “profitability”, “energy”, “water productivity”, “energy productivity”, “net return”, “production cost”, “cereal”, “India”, and the “Indo-Gangetic plain”. These words highlighted the results and policy framework aspects of maize research under CA systems.

For a better understanding of the word analysis, the word cloud [60] of keywords in the titles and abstracts of the screened publications was constructed as visualized in Figure 11, where the size of each word/phrase delineates its frequency/occurrence in research publications. It revealed that words like “soil”, “CA”, “conservation”, “agriculture”, “crop”, “tillage”, “system”, “practices” had the highest frequencies in research publications. The same frequencies are analyzed and presented in tree map form in Figure 12. Consequently, the co-word visualization analysis including the thematic network, word cloud, and tree map presented in the present study identified researchers pinpointing gaps in the literature, potential areas for future investigation, and the evolution of research paradigms. The visualization of the word analysis thus plays a vital role in synthesizing large-scale bibliometric data, supporting strategic research planning and informing academic and policy decisions.

3.2.4. Visualization of Organizations

The visualization of various stakeholders involved in conducting research on maize under CA systems viz., organizations and institutions using citation and co-citation analyses in bibliometric studies is vital for mapping the intellectual structure of a research field, illustrating how different entities are interconnected through scholarly communication, which enables the identification of key players with influential publications [61]. Additionally, it also facilitates the assessment of research impact and collaboration networks, offering insights into the productivity and influence of specific organizations and further bolstering the collaboration in strategic planning and decision-making for research funding and policy development, guiding institutions towards more impactful research directions [32].

The citation analysis of organizations or institutions involved in maize research under conservation agriculture between 2001 and 2023 was conducted by keeping the minimum documents associated with an organization at 5, and the resulting 199 institutions are visualized in Figure 13. The analysis resulted in six thematic clusters shaded with different colors. The “International Maize and Wheat Improvement Center” emerged as the most impactful organization in the current context of the study, with the highest number of citations (17,976) at 197 links/connections and a link strength of 13,823. Moreover, the organization “Indian Agricultural Research Institute” also had a significant impact in the research arena, with 3038 citations and 151 links. Overall, such a visualization of organizations provides a comprehensive overview of the knowledge diffusion and evolution of scientific disciplines, enhancing our understanding of how various stakeholders develop research areas and interrelate over time.

3.2.5. Visualization of Countries

The visualization networks of countries involved in maize research under CA systems using the citation analysis are crucial for revealing the global landscape of research collaboration and knowledge dissemination, highlighting leading countries and their interconnectedness [61]. Moreover, it also enables policymakers and funding bodies to make informed decisions by understanding the research impact and the collaborative dynamics among countries and fostering international cooperation by identifying potential partnerships and facilitating knowledge transfer between regions with varying expertise [62].

The citation analysis of countries involved in maize research under CA systems between 2001 and 2023 is presented in Figure 14, where each node represents a different country. Additionally, the size of each node signifies the sum of citations received by research publications originating from the respective country, and the different shades of color represent the thematic clusters [63]. There are five thematic clusters formed, with the United States having the highest number of citations received, followed by India and Mexico, with superior collaborative relationships with other counties. Additionally, visualizing these networks helps track the evolution of research trends over time, offering insights into how different countries contribute to the advancement of maize research under conservation agriculture systems.

In the thematic map, for maize crops under CA in Figure 15, niche themes represent high density (cohesive studies) but low centrality (weak connections) [64]. Within this quadrant, themes like agricultural systems, smallholder agricultural farmers, conservation agriculture, and cereal-based systems are developed, but their implications and connections to conservation practices are yet to be fully explored. The motor themes (high density, high centrality) are highly developed and well-connected to other themes, such as weed management, greenhouse gas emissions, and organic carbon in the Indo-Gangetic plains [6]. These themes are essential for understanding the overall field of conservation agriculture of maize crops and are mature in their internal development [17]. They often represent core, influential research areas with significant connections to other topics. Emerging or declining themes (low density, low centrality) represent either nascent fields with potential for future growth or outdated fields losing relevance, respectively. In this context, opportunities such as conservation agricultural practices in maize-based cropping systems are emerging [19]. The basic themes (low density, high centrality) often serve as foundational themes for broader research but may not be deeply explored themselves, such as long-term conservation in South Asia and maize cropping systems in agricultural systems [65]. The outcome of this thematic map helps researchers to identify which areas are worth exploring further, which are foundational, and which are likely to lead future research trends.

4. Discussion

The results of the present study displayed a steady increase in the number of publications in the first decade followed by an exponential upsurge in the next decade in the twenty-first century, indicating a significantly higher interest of researchers as well as stakeholders in the prospects of maize under CA systems. Research landscapes of maize under CA scenarios are gaining popularity due to their potential to enhance sustainability, resilience, and productivity in the context of rapid climate change [19,65]. CA practices, such as minimal soil disturbance, permanent soil cover, and crop rotation, improve soil health, structure, and fertility, which are crucial for maize’s water and nutrient needs [2]. These practices help retain soil moisture. On the other hand, maize requires much less water in its seed-to-seed stage, making maize more resilient to water stress and reducing soil erosion, which are vital under erratic climatic conditions [17,18]. Additionally, CA contributes to carbon sequestration and reduces greenhouse gas emissions, aligning with climate change mitigation efforts [3,14]. The focus on sustainable agricultural practices and the need to ensure food security drive the growing research interest in optimizing CA of maize, aiming to achieve high productivity and resilience in a warming world.

Research aspects on maize crops under CA systems are mainly focused on designing a climate-resilient production system with significantly lower ecological footprints such as carbon footprint, energy footprint, and water footprint vis-à-vis attaining food and nutritional security for the burgeoning population [66,67]. This is why the results underscore that the “agricultural, veterinary, and food sciences” research domain has the highest number of publications, followed by the “environmental sciences” domain. Additionally, a common roadmap for peace and prosperity for people and the planet, both now and in the future, is provided by the “2030 Agenda for Sustainable Development”, which was accepted by all United Nations Member States in 2015 [68]. The 17 Sustainable Development Goals (SDGs), which represent an urgent call to action for all nations—developed and developing—in a global partnership, are at the center of it. Maize has provided a wider avenue for fulfilling the food and feed demands due to its higher productive potential coupled with its lower environmental impact as compared to conventionally cultivated crops like lowland rice and other cereals [69]. This leads to the fulfillment of SDGs like “SDG 2: Zero Hunger”, “SDG 15: Life on Land”, and “SDG 13: Climate Action”.

Moreover, the researchers Christian L. Thierfelder and Mangi Lal Jat emerged as the most impactful authors with 4753 and 4504 citations [70], respectively, for 88 documents each (Table 2). Christian Thierfelder holds 9658 Google Scholar citations [71], with an h-index [72] of 50 on his account, serving as a “Principal Cropping Systems Agronomist” with CIMMYT’s Sustainable Intensification program and spearheading research on CA systems in Southern Africa, aiming to tailor these systems to the unique needs and environments of smallholder farmers. His current work involves refining CA practices for various agro-ecological zones and investigating the adoption of new technologies by farmers, which includes the integration of green manure cover crops and grain legumes into maize-based farming systems, promoting climate-smart agriculture and the agro-ecological management of fall armyworm [30,73,74]. His research is primarily conducted in Malawi, Zambia, and Zimbabwe, with some activities in Namibia. Similarly, Mangi Lal Jat, with 19,020 Google Scholar citations [71] and an h-index [72] of 74 on his account, is a cropping system agronomist and has a significant number of publications in developing system optimization practices in maize under CA systems focusing mainly on precision nutrient management, crop diversification options, environmental footprint analysis, etc. [75,76,77]. Prominent researchers such as Christian L. Thierfelder, M. L. Jat, Bram Govaerts, Marc Corbeels, and Rattan Lal are notable citation leaders in various clusters in the citation and co-citation visualization network, making substantial contributions to maize research under CA. Co-authorship is considered one of the most measurable and thoroughly documented forms of scientific collaboration, leading to the development of a “co-authorship network” to develop new vistas of research on maize under CA systems.

The current bibliometric study indicated that the journals “Soil and Tillage Research”, “Field Crops Research”, and “Agriculture Ecosystems & Environment” were the three most impactful published in the research domain of maize under CA systems. The journals viz., “Soil and Tillage Research”, “Field Crops Research”, and “Agriculture Ecosystems & Environment” have an impact factor [78] of 6.5, 5.8, and 6.6 along with a cite score [79] of 12.7, 9.6, and 10.2, respectively. All three journals published by Elsevier [80] are very impactful and contribute significantly to the advancement of agricultural sciences by publishing significant achievements in pertaining to soil management, crop production, and the environmental implications of agricultural practices, thereby supporting the development of sustainable and resilient agricultural systems [81,82]. The citation analysis of sources revealed that there were more citations received by Elsevier’s published journals such as “Field Crops Research” and “Soil and Tillage Research” in the 2016–18 phase, but in recent times (2020 onwards), more publications have appeared in journals like “Sustainability (MDPI)”, “Scientific Reports (Nature)”, and “Frontiers in Agronomy” because of faster processing and open access [83] publishing gaining more interest among researchers and stakeholders publishing their articles related to maize research. These recently popularized journals also receive higher numbers of citations and cite scores due to their easy searchability in different web search engines [84]. Similarly, the co-citation analysis of journals forming different clusters of being cited together is crucial for uncovering the intellectual structure of research fields by identifying how often pairs of articles are cited together, thereby highlighting influential studies and key areas of knowledge integration [48].

Using word analysis visualization in bibliometric studies, researchers can identify prevalent topics, emerging themes, and shifts in research focus to understand the thematic essence and research trends within a body of literature by mapping the frequency and co-occurrence of words in titles, abstracts, and keywords [52,53]. This method transforms complex textual data into interpretable formats like thematic networks and word clouds, providing quick insights into the main subjects and their interconnections [60]. The present word analysis revealed the presence of three clusters mainly delineating the orientation of maize research under CA systems primarily revolving around three broad topics viz., key drivers of maize research under CA, objectives and methodology along with treatments, and the implications of maize research on farm and global scales. The word analysis suggested that the key drivers are climate change, technology adoption among farmers, resource optimization, crop diversification, and soil erosion, whereas the objectives and methodologies involve entities such as tillage practices, crop residue management [15], yield enhancement, carbon analysis [12], cropping season intensification [85], and nitrogen management under CA [54]. The broad implications of maize research under CA comprises farm profitability, resource use efficiency, water productivity [11], energy productivity [23], cereal intensification through legume inclusion, etc., providing significant insights into the frontier areas of research and innovation [65].

Visualizing the various stakeholders, including organizations and institutions, involved in maize research under CA using citation and co-citation analyses in bibliometric studies is crucial for mapping the intellectual structure [32] that illustrates the interconnectedness of different entities through scholarly communication and enables the identification of key players with influential publications [31]. It facilitates the assessment of research impacts and collaboration networks among specific organizations for strategic planning, decision-making, and policy development, guiding research in more impactful directions [86]. The present analysis revealed six thematic clusters in different colors, with the “International Maize and Wheat Improvement Center” emerging as the most impactful organization followed by the “Indian Agricultural Research Institute”, with 17,976 and 3038 citations [70] and 197 and 151 links [31], respectively. This visualization provides a comprehensive overview of knowledge diffusion and the evolution of scientific disciplines, enhancing our understanding of how various stakeholders develop and interrelate over time.

The “International Maize and Wheat Improvement Center (CIMMYT)” has a pivotal role to play as it develops sustainable farming practices that improve food security and environmental health. CIMMYT’s efforts also extend to developing high-performing drought-tolerant maize varieties for CA systems with the aim of increasing climate adaptability involving extensive on-farm experimentation with farmers at particular sites to adapt such practices according to specific needs so as to enhance their rates of adoption [87]. Moreover, CIMMYT leads flagship collaboration with agricultural research systems of various nations, universities, and other international organizations to scale up the CA research impact on the sustainability and productivity of maize amidst climate change challenges. Similarly, the Indian Agricultural Research Institute (IARI) also plays a lead role within the context of the Indo-Gangetic plain, which was hampered by rapid soil degradation and significant environmental challenges [88]. As per the documents published, certain disciplines of the IARI under the school of natural resource management such as “agronomy”, “soil science and agricultural chemistry”, and “environmental science” have led comprehensive research, especially focusing on crop diversification options involving maize [15], enhancing soil health [12], reducing energy and environmental footprints [65], and system productivity [23] by conducting field trials under long-term CA systems that contribute to the resilience of maize, addressing food security concerns and environmental protection at large.

Additionally, the visualization of countries in the present investigation delineated five thematic clusters of collaborations, where the United States had the highest number of citations received followed by India and Mexico, as well as superior collaborative relationships with other counties. This might be due to the presence of institutes like the CIMMYT and IARI in the United States and India, respectively, and the policy decisions of the countries towards designing more sustainable agri-food systems. Therefore, the network visualization of the countries aids in monitoring the progression of research trends over time along with the contributions of different countries in the refinement and advancement of research ideas pertaining to maize under CA systems [61].

5. Implications and Future Prospects

The research and production of maize under CA systems holds enormous implications and revolutionary trends, specifically in the context of global food security, environmental sustainability, and climate resilience (Figure 16). By encompassing the principles of lesser soil disturbance, perennial soil cover, and diversified crop rotation with maize as the main component crop, CA offers multifaceted solutions to some of the pressing challenges of modern-day agriculture [3]. CA improves the physical and biological properties of the soil, as the minimization of soil disturbance reduces the oxidation of organic carbon, soil erosion, and soil compaction, which contributes positively to higher and more stable maize productivity [7,12]. Maize under CA has enhanced the water use efficiency as CA increases soil moisture retention with less evapotranspiration due to retained residue, and maize as a C₄ crop requires less of a water footprint to produce a higher biomass or economic yield [10,11]. Further, maize under CA practices reduces the negative effects of climate change by conserving and enhancing the storage of soil carbon, as well as enhancing soil fitness in cases of unfavorable climate conditions as compared to other cereal-based cropping seasons [13,89]. This approach also fosters conservation and diversification, or bio-diversity, which benefits supporting services like pest control and nutrient cycling for the enhancement of ecological resilience [90]. Additionally, it also promotes reduced input costs through CA with system optimization practices such as legume inclusion and precision input management, improving yield stability and increasing maize production through the use of advanced hybrids that have more adaptability and productivity, ensuring global food security amidst likely fluctuating climate conditions and declining land per capita [22,25,26].

It is clear that maize research under CA systems holds greater future prospects that seem more promising and multifaceted (Figure 16). The inclusion of advanced precision input management technologies with standard machinery fitted well to CA systems can enhance the effectiveness of CA practices, uplifting its resource use efficiency and making it more scalable [65,91]. The advanced genetic improvements in maize varieties tailored to CA can enhance traits such as biotic and abiotic stress tolerance, enhancing its acreage to resource constraint areas [26]. Apart from the huge scope in the value addition of various types of maize, its increasing use day by day for non-conventional industrial purposes like biofuel will increase the maize demand in the global market, putting enormous pressure on agri-food systems to produce more and more [21]. The proper implementation of policy support for CA, professional education, and capacity building for consensus are essential for the widespread adoption of CA, with the provision of incentives alongside robust monitoring systems for tracking the penetrability of technologies and impact assessment [92]. Enhancing ties with global and local sources of knowledge as well as focusing on long-term commitment to sustainability and pursuing research towards adaptive management solutions will further fortify CA’s role in environmental conservation, achieving more SDGs.

6. Conclusions

The current bibliometric analysis of the maize research landscape within the framework of CA discloses an evolving field marked by substantial scholarly contributions and concerted efforts. As per the objective of our study, this inclusive examination accentuates the multifaceted benefits of CA particularly in enhancing soil quality, improving resource use efficiency and bolstering the resilience of maize cultivation against rapid climate change. The number of articles published under each research areas such as “agricultural, veterinary, and food sciences”, “environmental sciences”, “human society”, and “biological sciences” laid out the importance of maize research under CA for holistic development. The findings provide a detailed mapping of the research landscape highlighting key SDG themes, influential journals, leading researchers, and emerging trends, which press upon the urgent need of the given topic in the present scenario. The global distribution and collaborative cluster identified the United States, India, and Mexico as leading countries and the CIMMYT and the IARI as the key institutions/organizations supporting maize research under the various avenues of CA, which explain the scope of the present study on the global scale and the urgent need of sustainable crop management practices like CA systems. The thematic analysis of keywords revealed soil health, crop productivity, and sustainable farming practices as the core areas reflecting the foundational principles of CA systems. Additionally, trends such as the cropping system optimization practices encompassing the inclusion of legumes in maize systems coupled with precision input management and region-specific CA adaptations suggest a move toward tailored, technologically advanced maize cultivation approaches. Strong ties between stakeholders and key players in developed and developing countries indicate a shared commitment to addressing global food and nutritional security challenges. The visualization of the maize potential within the broad avenues of CA in the present study offers valuable guidance for the future research base, policy development, and implementation with identified trends, key contributors, and collaborative networks playing crucial roles in advancing sustainability maize cultivation, especially under the broad umbrella of CA frameworks, ultimately contributing to global food security and conserving the natural environment.